The present invention relates to a plasma display panel (PDP), and more particularly to a barrier rib structure for preventing error discharge and improving luminescence efficiency.
Plasma display panels (PDP) can be divided into two types, the direct current (DC) type and the alternating current (AC) type, according to their electrical driving mode. In FIG. 1, which illustrates a conventional AC-type PDP, glass plates 11, 12 undergo several manufacturing steps in which many functional layers are formed thereon and are then combined together by sealing the periphery of the glass plates 11, 12. A mixed gas with a predetermined ratio is then introduced into the discharge units between the glass plates 11, 12.
In FIG. 1, a plurality of parallel transparent electrodes 111 and bus electrodes 112, a dielectric layer 113 and a protective layer 114 are sequentially formed on the glass plate 11, hereinafter referred to as front plate 11. Similarly, a plurality of parallel address electrodes 121, a plurality of parallel barrier ribs 122, a fluorescencer 123 and a dielectric layer 124 are formed on the glass plate 12, hereinafter referred to as back plate 12. One transparent electrode 111 on the front plate 11 and one address electrode 121 on the back plate 12, transparent electrode 111 and address electrode 121 being perpendicularly crossed, compose a discharge unit. When a voltage is applied to a specific discharge unit, gas discharge occurs at the discharge unit between the dielectric layers 113 and 124 to induce emission of a colored visible light from the fluorescencer 123.
FIG. 2 is a schematic, cross-sectional view corresponding to FIG. 1. In a conventional AC-type PDP 10, referring to FIGS. 1 and 2 simultaneously, a plurality of parallel-arranged transparent electrodes 111 are formed on the front plate 11. Each of the transparent electrodes 111 correspondingly has a bus electrode 112 to reduce linear resistance of the transparent electrodes 111. In one discharge unit 13, a three-electrode structure, including an X electrode and an Y electrode of the transparent electrode 111 on the front plate 11 and an address electrode 121 on the back plate 12, is generally employed. When a voltage is applied to the above three electrodes of a specific discharge unit 13 to induce discharge, the mixed gas in the discharge unit 13 glows ultraviolet (UV) rays to light the fluorescencer 123 inside the discharge unit 13. The fluorescencer 123 then emits a visible light, such as a red (R), green (G) or blue (B) light. An image is thus produced by scanning the discharge unit array.
In the conventional AC-type PDP 10, the barrier ribs 122 are arranged in parallel strips on the back plate 12. The address electrode 121 between two adjacent barrier ribs 122 is disposed inside the dielectric layer 124. In the structure, the fluorescencer 123 can only be coated on the sidewalls of the barrier ribs 122 and the top surface of the dielectric layer 124, so that only three planes are utilized. In each discharge unit 13, the fluorescencer 123 is coated on a small surface area, so that a low luminescence efficiency is obtained in the conventional PDP 10.
Since an erroneous discharge may occur in a non-discharge unit 13a, illustrated in FIG. 3, of the conventional AC-type PDP 10, the distance d between two adjacent discharge units 13 must be increased to prevent the same. Although a larger non-discharge unit 13a prevents erroneous discharge, discharge units 13 are then relatively contracted, i.e. have a reduced opening ratio, and luminescence efficiency is thus decreased. Conversely, a smaller non-discharge unit 13a provides larger discharge units 13, but erroneous discharge then readily occurs, so that neighboring discharge units 13 are affected during operation.
In addition, no isolation is provided between the discharge region A and non-discharge region B and erroneous discharge thus readily occurs in the non-discharge region B. A conventional method for solving the erroneous discharge issue in non-discharge region B is to perform an additional treatment of forming black strips to shade a light produced in the non-discharge region B. The contrast of the conventional PDP 10 is therefore increased, but further manufacture cost is incurred.
To solve the foregoing described problems, several different kinds of barrier rib structure have been developed by PDP designers and manufacturers. For example, Pioneer Company provides a Waffle structure having sealed latticed barrier ribs. The fluorescencer can be coated on the five planes of each discharge unit, i.e. front, back, left, right and bottom planes, thereby improving luminescence efficiency by increasing the fluorescencer coating area. At the same time, each discharge unit becomes a closed space and this effectively prevents erroneous discharge in non-discharge units. Unfortunately, the closed discharge units result in greater difficulties when vacuuming and refilling gas during the manufacturing processes.
According to the above descriptions, for the barrier rib structure of a conventional PDP, many drawbacks occur; for example, the structure is prone to erroneous discharge, the luminescence efficiency is low, or the structure is hard to vacuum. Therefore, the present invention provides a barrier rib structure for a plasma display panel (PDP) that can resolve above problems.
It is an object of the present invention to provide a barrier rib structure where a plurality of nodes composed of two side-expanded trapezoid bulges are designed in non-discharge regions of barrier ribs to form small gas channels between the nodes. The small gas channels can inhibit unsuitable discharges in non-discharge regions during gas discharging to prevent erroneous discharge. Moreover, by controlling erroneous discharge, the margin of driving voltage can be increased, so that the yield of products can be improved. Furthermore, the small gas channels in non-discharge regions are helpful to gas purging and refilling during manufacture of a PDP device.
It is another object of the present invention to provide a barrier rib structure where a plurality of nodes composed of two side-expanded trapezoid bulges are designed in non-discharge regions of barrier ribs. The error discharge problem can be effectively prevented, so that the area of non-discharge regions can be diminished to increase the area of discharge regions. Therefore, the opening ratio can be increased, and the luminescence efficiency can be improved. The trapezoid bulges of the present invention add four tilted planes at the corners of each discharge unit. Accordingly, the fluorescencer coating area of each discharge unit is increased, and thus the luminescence efficiency is improved.
It is a yet another object of the present invention to provide a barrier rib structure that forms an almost closed discharge space to constrict energy in the discharge space as well as gas discharge, and this structure is helpful in utilizing gas discharge energy. Furthermore, the corners of the discharge space are designed as inclined planes or arced planes that improve uniform reception of ultraviolet rays by the fluorescencer to increase luminescence from the fluorescencer.
It is a further object of the present invention to provide a barrier rib structure that further comprises an isolation wall adjacent to a purge hole. The isolation wall is perpendicular to the gas channels to stop the gas from flowing straight into the purge hole, so that local disturbed gas flow can be minimized to prevent damage to the barrier ribs adjacent to the purge hole.
In one aspect, the present invention provides a barrier rib structure on a back substrate for a plasma display panel. The structure at least comprises a plurality of barrier ribs. Each barrier rib has a plurality of nodes in series composed of two side-expanded trapezoid bulges. The barrier ribs are in a parallel arrangement corresponding to the nodes to form a plurality of discharge spaces between the barrier ribs and a plurality of gas channels between the nodes. The gas channels connect neighboring discharge spaces.
In another aspect, the present invention provides a gas discharge luminescent structure for a plasma display panel. The structure at least comprises a first dielectric layer, a plurality of barrier ribs, a fluorescent layer and a second dielectric layer. The first dielectric layer has a plurality of parallel address electrodes therein. The barrier ribs are formed on the first dielectric layer, and respectively disposed between the address electrodes. Each barrier rib has a plurality of nodes in series comprising two side-expanded trapezoid bulges. The barrier ribs are in a parallel arrangement corresponding to the nodes to form a plurality of discharge spaces between the barrier ribs and a plurality of gas channels between the nodes. The fluorescent layer is coated on the inside wall of the discharge space. The second dielectric layer is located on the barrier ribs to seal the discharge space. The second dielectric layer has a plurality of parallel transparent electrodes therein. The transparent electrodes and the address electrodes cross in the discharge space.
The transparent electrode can comprise an X electrode and an Y electrode. Each of the X and Y electrodes has a bus electrode, respectively. By applying a voltage to these electrodes, a mixed gas sealed into the discharge space generates ultraviolet rays to light the fluorescent layer such that the fluorescent layer emits the desired colored visible light.